Calcium carbonate (calcite) is found in limestone rock along with various mineral impurities, particularly silicates such as, quartz, mica, feldspar, etc. The most common known methods for separating the calcite from the mineral impurities involve physical separations whereby the limestone rock is first ground and slurried and the ground material is subject to floatation by employing some means which selectively imparts hydrophobicity to certain of the components of the rock to enable such components to be floated away. In the reverse flotation process it is the impurities which are floated away from the calcite.
Means to provide hydrophobicity to the impurities in the reverse flotation process are numerous and well known to the art, including, from U.S. Pat. No. 3,990,966 to Stanley et al, 1-hydroxyetyl-2-heptadecenyl glyoxalidin, 1-hydroxyethyl-2-alkylimidazolines and salt derivations of the imidazoline. Canadian Publication No. 1187212 discloses, the following quaternary amines or salts thereof for use as collectors: dimethyl dialkyl with the alkyl groups containing 8 to 16 carbon atoms and being optionally unsaturated and optionally branched; and dimethyl alkyl benzyl with the alkyl containing 10 to 22 carbon atoms and being a normal aliphatic; and bis-imidazoline containing 12 to 18 carbon atoms in optionally unsaturated normal alkyls.
Another collector in common use is a combination of N-tallow-1,3-diaminopropane diacetate (Duomac T) and a tertiary amine having one long carbon chain alkyl group and two polyoxyethylene groups attached to the nitrogen (Ethomeen 18/60). The latter compound serves as a dispersant. A significant disadvantage to the use of this combination is that both compounds of the combination are high melting points solids and to be used must be dispersed in water with a high energy blender and/or heating and then mixed so as to remain in suspension.
Arquad 2C (dicocodimethylammonium chloride) is also a known collector, but it requires an alcoholic solvent system to facilitate its manufacturing process which can cause flammability problems during manufacturing, storage and use of the product. This product also has a relatively high pour and cloud point.
We have discovered certain organo-nitrogen compound collectors which are at least as effective as known prior art collectors, and better than most, but which are able to function as single liquid collectors and which are relatively inexpensive to manufacture and readily available.